Reseal members or reseals are in wide-spread use in the health care industry on liquid containers, and such reseals typically accommodate the insertion of a needle or cannula through which liquid can be added or withdrawn from the container.
Typically, reseals are used on containers such as vials or flexible bag-type containers of liquids such as medicaments or parenteral solutions and the like. Such reseals are also incorporated in Y-sites of tubing sets for infusion. The reseals provide easy access to the solution or other liquid by use of a hypodermic needle or cannula which punctures the reseal and which is inserted therethrough.
Reseals are typically fabricated from natural rubber. This material has the inherent property of retaining its shape after it is punctured. As such, it provides an excellent seal for a container subsequent to initial puncture when the cannula is inserted and even after the cannula is withdrawn.
Some conventional reseals have a completely solid membrane which must be punctured by the cannula. Other conventional reseals are pre-slit to facilitate cannula penetration. The type of reseal with a solid membrane is, of course, preferably used in those applications wherein the likelihood of contaminant ingress must be minimized as much as possible.
In order to minimize the likelihood of punctures in a person's skin resulting from misuse of sharp cannulas in the performance of health care procedures, the use of "blunt," relatively unsharpened cannulas is becoming increasingly prevalent. One of the design criteria which must be accommodated in connection with the use of blunt cannulas relates to the piercing force required to insert the cannula through a reseal. Typically, a substantial force must be applied to the blunt cannula to puncture the reseal, especially, the type that is not pre-slit.
In order assist the user in properly puncturing and penetrating the reseal with a blunt cannula, it has been determined that the central portion or membrane of the reseal may be provided with a partial slit according to the principles of the present invention. In particular, a slit extends from the inner surface of the reseal membrane, but only partially through the thickness of the membrane.
A sufficient thickness of the membrane is left uncut to provide the necessary sealing function and to provide sufficient resistance to penetration for preventing inadvertent puncturing of the reseal. A partial slit will allow the unslit portion of the reseal membrane to function initially as an effective barrier against contaminant ingress. The partial slit permits a thicker membrane to be used so that after puncture by the cannula, there is a sufficient thickness of material to provide adequate or enhanced sealing and resistance to contaminant ingress either with the cannula inserted or with the cannula withdrawn.
The partial slit or cut extending from the inner surface of the reseal membrane weakens the membrane and provides a preferential puncture region as the membrane is deformed inwardly by the tip of the blunt cannula.
More particularly, the penetrating cannula stresses the reseal membrane until the ultimate stress in the uncut thickness of material is reached. At that point, the uncut portion of the reseal membrane ruptures, and the cannula passes through the reseal membrane.
The process by which the blunt cannula penetrates the reseal membrane is dependent upon the reseal membrane thickness, the depth of the partial perforation or slit, the elastic modulus of the material, the lubricity of the material, the size and shape of the cannula, and other factors. For a given set of values for these parameters, it is desirable to provide a reseal design wherein all of the reseals of that design will require substantially the same force to achieve penetration by a blunt cannula. This will permit the reseal manufacturer to be more certain of the integrity of the reseal as manufactured. Also, this will be helpful to the user who can learn to expect that a particular amount of force will be required to puncture a particular type of reseal with the cannula.
One of the factors which significantly affects the puncturing force required is the thickness of the uncut or unslit portion of the reseal membrane above the partial perforation or slit. Because the reseal membrane is an elastic material, typically a natural rubber, the manufacturing of the membrane with a specific membrane thickness and a specific uncut thickness below the initial, partial perforation is difficult from the standpoint of providing a uniform or consistently identical structure in each reseal that is manufactured.
In particular, the partial perforation is formed in the reseal membrane by moving a lance or other cutting edge partially into the reseal membrane. Due to manufacturing tolerances in the molding of the membrane and the resilient nature of the membrane material, the thickness of the uncut material in the membrane above the partial perforation or slit could vary from reseal to reseal. Accordingly, it would be desirable to provide a system for more accurately controlling the thickness of the uncut material in the reseal membrane above the partial perforation.
It would also be advantageous to provide the capability for creating different partial perforation configurations in the reseal membrane. For example, it would be desirable to provide improved, larger partial perforations that establish a larger or specially defined target area.
It would also be beneficial if an improved partial perforation configuration could be provided with enhanced sealing capabilities.
The present invention provides an improved reseal, a method for making the reseal, and an apparatus for making the reseal which can accommodate designs having the above-discussed benefits and features.